mini-gmp request for version inclusion

[Simon Sobisch]

I don't know how often mini-gmp is updated and it is possibly not
reasonable to increase its version number along with GMP, but currently
there is no version number available at all.

We can already test for use of mini-gmp via __MINI_GMP_H__ (defined by
both mini-gmp.h and mini-gmp.c) but there's no version number available.
Feature request: add *defines* __GNU_MP_VERSION and
__GNU_MP_VERSION_MINOR and a macro for gmp_version in both gmp-mini.h
and gmp-mini.c  (possibly also in mini-mpq.c/h).

Thank you for considering this,
Simon Sobisch